When welding sections of pipe together to form a pipeline, or the like, it is usually necessary to have some mechanism to hold the abutting ends of the pipe sections to be welded in precise relation to each other to allow formation of a proper weld. The holding and aligning mechanism can be exterior the pipe sections, but this often interferes with the welding operation, which is typically done exterior the pipe sections as well. Over the years, internal pipe aligning mandrels or clamps have been developed for pipes which are actually inserted into the interior of the pipe sections to clamp and align the pipe sections. These mandrels often include air or hydraulically driven radial pistons which move outwardly from the mandrel into contact with the interior surface of the pipe sections to perform the alignment. While such mandrels are effective in use, they are complex and heavy structures which require careful placement within the pipe sections and constant maintenance and service to ensure proper function.
Several years ago, an internal bending mandrel was developed by the assignee of the present application which resulted in U.S. Pat. No. 4,731,203. This mandrel utilized urethane discs which were resiliently deformed by a hydraulic cylinder to expand outward into tight frictional contact with the inner surface of a pipe being bent. The pipe could then be placed in a pipe bending apparatus and bent without collapsing the walls of the pipe. The present invention contemplates the use of advantages provided by such a resilient internal mandrel in the environment of alignment and clamping of pipe sections to be welded.